Board Game Arena

Hello,
The rulebook says you can swap the plants but how does this work? No details about that. Wouldn't it be against the rules if I swapped a Level 1 plant with Level 2 or 3 plant without watering it? Does it only work when we swap a higher level plant with the lower level (let's say I have a Level 4 plant and I can change it with a Level 3 plant) ?

if you want to put a new plant into a spot that has a plant, you can.
You can throw away a yellow and plant a blue, or throw away a blue and plant a yellow.
You can always throw away a plant and plant a different one if your action gives you a plant to play with.